Kapture Group do a triple stitch, which I think would be useful on a P3 with a 60Mpx back, as you could get about 53 * 90 mm, with plenty of overlap for stitching, giving about 134Mpx, which should be pretty useful for landscapes, without losing pixels or res through distortion.
If they do the quad stitch for the P3, you would not get much advantage over the triple shift except for with smaller sensors... with a 31Mpx 33 * 44mm sensor you could neatly cover the 6*9 cm, but the software might like more overlap for auto-aligning
¿anyone tried it?
With slide and stitch we might not need that much overlap, so a stitching back for a P2 might be a better option: Many of the Apo-digitars do not give enough image circle to use the extra area.
Using camera rise/fall/shift for stitching would work, but, if you use rear fine tilt and then shift to stitch, you would lose focus ... the way round this with a "proper" camera like a Sinar is to use coarse (standard) tilt for perspective, and leave the fine rear tilt at zero. This would not help for horizontal shift-and stitch, unless you turned the camera through 90 degrees.